These studies are part of a project to study the regulation of respiration in patients with a diminished ventilatory response to CO2 and hypoxia. During the coming year, we will work on the following aspects of this project: 1. The effect of resistive loads on ventilatory drive in patients with interstitial lung disease, obstructive lung disease, and normal subjects. 2. The treatment of dyspnea with tranquilizers and possibly other drugs that suppress chemical ventilatory drive. 3. The interaction of chemical and neural regulation of respiration in patients with strokes and animals with discrete brain stem lesions. 4. Follow-up studies on the effects of long-term continuous oxygen therapy on hypoxic ventilatory drive.